Solutions of polyesters in substituted phosphoric amides and process for making same



SOLUTIONS OF POLYESTERS IN SUBSTITUTED- PHOSPHORIC AlVIlDES MAKING SAME Arthur B. Beindorlf, Decatur, Ala., and Hobson D. De

Witt, New Wilmington, Pa., assignors to .The Chemstrand Corporation, Decatur, Ala., a corporation of Delaware No Drawing. Filed Sept. 4, 1958, Ser. No. 758,907

20 Claims. (01. zen-30:6

AND PRQCESS FOR be described as it is applied in the manufacture of fibers and filaments. However, the invention is not to be lim-' ited thereby except insofar as it may be limited by the appended claims.

.Various methods are known for converting the polyesters described above into filaments and fibers, such as the so-called melt-spinning, wet-spinning and dry-spinning methods.

Melt-spinning comprises melting chips of a polyester on a heated grid and passing the melt through a filter bed of small particles, such as sand, and the like. Subsequently, the melt is forced through a spinneret and the filaments so-formed are cooled. However, melt-spinning has certain disadvantages such as the employment of high temperatures which makes the addition of plasticizers and modifying agents difiicult, because there is a tendency for, the added agents to discolor. and decompose.

. In the dry-spinning method the polyester is dissolved in a solvent therefor and extruded through a spinneret in the The solution is extruded into an atmosphere of mert gas which may be heated. The motion of usual manner.

the inert gaseous atmosphere, the extruded fiber and the application of heat all aid in disposing of the volatile solvent.

The wet-spinning method in which a solution of polyester is extruded into a bath containing a non-solvent for the polyester has a number of advantages over the melt-spinning method. For example, the wet-spinning method is generally more economical and can be carried.

out at lower temperatures. Therefore, plasticizers and other agents may be added with a minimum tendency toward discoloration and decomposition. Furthermore, certain types of plasticizers and modifying agents tend to be less compatible for blending in amelt at high temperatures, whereas they can be readily incorporated in a polyester solution at a low temperature. Solutions offer the further advantage in that they may be easily cast into films or coatings of uniform thickness. This is extremely difiicult with a molten composition because of its relatively high viscosity.

The wet-spinning technique, however, has not been employed commercially because of the lack of suitable solvents. Generally polyesters are insoluble in the more common organic solvents. From the standpoint of low cost, solvent power, non-corrosiveness and ease of recov- 2,952,652 Patented Sept. 13, 1960 ery, there is a scarcity of suitable solvents for the more usual types of polyesters.

Accordingly, the principal object of the instant invention is the preparation of polyester solutions or dopes which are capable of being transformed into shaped articles.

Another. object is to provide synthetic linear condensation polyester compositions in solutions which are stableand have non-gelation characteristics.

solutions of polyester compositions.

Other objects and advantages of the invention will be apparent from the following description.

The foregoing objects are accomplished by dissolving the synthetic'linear condensation polyester in compounds such as substituted phosphoric amides having the general formula,

/CH: RIIN\ /N\ CHa I CH3 CH3 7 wherein R is CH N(CH or i (CHs)2--N\(? (CH3)2N Among such compounds are tris (dimethylamido) phate, bis (dimethylamido) methane phosphonate, bis (dimethylamido) ethane phosphonate, amido) pyrophosphate. V r

Solutions of high solids content and good stability can be prepared by mixing the polyester in the substituted phosphoric amides and heating to a temperature in a range of C. to the boiling point of the mixture. If desired, the mixture may be stirred while heating. However, stirring is not necessary to elfect solution, although it has been found that the polyester goes into solution formed is to be used as a coating or as a lacquer. In preparing solutions or dopes suitable for spinning into filaments and fibers, 10 to 20 percent by weight of the polyester, based on the total weight of the solution, is

suitable. While it is preferred to employ 10 to 20 percent by weight, based on the total weight of the solution, of the polyester in the solvent when the solution is to be used for the preparation of fibers and filaments, it is to be understood that as little as 5 percent or less and as much as 25 percent or more of the polyester may be utilized when the solution is to be employed for other purposes, such as coating or lacquer and the'like, or when lower or higher molecular weight polyesters are to be dissolved in the new solvents of the invention. The amount of any specific polyester, which can be dissolved in the solvents of this invention, will be readily evident to those skilled inthe art.

The synthetic linear condensation polyesters contem.

plated in the practice of the invention are those formed from dicarboxylic acids and glycols, and copolyesters or.

modifications ofthese polyesters and copolyesters. In a highly-polymerized condition, these polyesters and co phostetrakis (dimethyI- Lower molecular weight polyesters may be utilized when the solution to be 3 polyesters can be formed into filaments and the like and subsequently oriented permanently by cold draining. The polyesters and copolyesters sepcifically useful in the instant invention are those resulting from heating oneor. more of the glycols of the s'eries.HO(CH .-OH, in'.

which n is an integer from 2 to 10, with one'or more dicarboxylic. acids .or. ester-forming derivatives thereof, Among the dicarboxylicacids and ester-forming derivatives thereof useful in the present invention there may be named terephthalic acid, .isophthalic acid, sebacicfacid, adipic acid, .p-carboxyphenoaceticacid, succinic acid,

' p',p-dicarboxybiphenyl,p,p'-dicarboxycarbanilide, p,p'-dicarboxythiocarbanilide, p-,p dicarboxydiphenylsulfone,

p-carboxyphenoxyacetic acid, p-carboxyphenoxypropionic.

acid, p-carbox-yphenoXybutric acid, 'p-carboxyphenoxyvaleric acid, p-carboxyphenoxyhexanoic acid, p-carboxyphenoxyheptanoicacid, .p,'p'edicarboxydiphenylmethane, p',p'-dicarboxydiphenylethane, p,1,r-dicarboxydiphenylpropane, .p,p' dicarboxydiphenylbutane, p,p dicarboxydiphenylpentane, p,p-dicarboxydiphenylhexane, p,p'-dicarboxydiphenylheptane, p,p' dicarboxydiphenyloctane, p,p'-dicarboxydiphenoxyethane, p,p'-dicarboxydiphenoxypropane, p,p-dicarboxydiphenoxybutane, p,p'-dicarboxy- 'diphenoxypentane, p,p-dicarboxydiphenoxyhexane, 3-al-.

kyl 4-(beta-carboxy ethoxy) benzoic acid, oxalic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid and the dioxy acids of ethylene dioxide having the general formula, f

wherein It is an integer from 1 to 4, and the aliphatic and eycloaliphatic aryl esters and half esters, ammonium and amine salts, and the acid halides of the above-named compounds and the like. Examples of the glycols which may be employed in practicing the instant invention are ethylene glycol, trimethylene glycol, tetramethylene' gly-v with chain terminating groups having hydrophilic propcries, such as the monofunctional ester-forming polyethers bearing the general formula,

wherein R is an alkyl group containing 1 to 18 carbon atoms or an arylgroup containing 6 to 10 carbon atoms, and m and n are integers from 2 to 22, and x is a whole number indicative of the degree of polymerization, that is, x is an integer from 1 to 100 or greater. Examples of such compounds are methoxypolyethylene glycol, ethoxypolyethylene glycol, n-propoxypolyethylene glycol, ism propoxypolyethylene glycol, hntoxypolyethylene glycol, phenoxypolyethylene glycol, methoxypolypropylene glycol, methoxpolybutylene glycol, phenoxypolypropylene glycol, phenoxypolybutylene glycol, methoxypolymethylene glycol, and the like. Suitable polyalkylvinyl ethers having one terminal hydroxyl group are the addition polymers prepared by the homopolymerization of alkylvinyl ethers wherein the alkyl group contains from 1 to 4 carbon atoms. Examples of such chain-terminating agents It is to be noted that when chain-terminating agents are employed alone, i'.e., without a chain-branching agent, the maximum amount that can be employed in the reaction mixture is 1.0 mol percent. Thus, unexpectedly, the addition of controlled amounts of chain-branching agents along with the chain-terminating agents allows the introduction of an increased amount of the'latter into the polyl mer chain than isotherwise possible when employing the agent.

chain-terminating agents alone.

One will readily appreciate that the Weight percent of chain-terminating agent which may be employed in this invention will vary with-the molecular weight of the The range of average molecular weights of the chain-terminating agents suitable for use in this invention is from 500 to 5000, with those agents having a molecular weight in the r nge 0151000 to 3500 being preferred.

Materials suitable as chain-branching agents or crosslinkingagents, which are employed to increase the viscosity or molecular weight of the polyesters, are the polyoIs which have av functionality greater than two, that is, they contain more than two functional groups, such as 1 hydroxyl. Examples .of suitable compounds are pentae'rytliritolico'mpounds having the formula:

( Q n i wherein R is an alkylene group containing from '3 to 6 carbon atoms and n 'is an integer from :3 to 6, for ex I ample, glycerol, sorbitol, hexane -trioll,'2,

and the like{ compounds having the formula: i7 I i z H)a' wherein R is an alkyl group containing fromz to 6 carbon 7 atoms, for example, trimethylolethane, trimethylol pro-' and in which R, R' and R" are alkyl groups containing are, hydroxy polymethylvinyl ether, hydroxy polyethylvinyl ether, hydroxy polypropylvinyl ether, hydroxy poly-. butylvinyl ether, hydroxy polyisobutylvinyl .ether,and The chain-terminating agents or compounds the like. may be employed in the preparation of the modified polyor dialkyl ester thereof employed in the reaction mixture;

copolyesters' described herein.

1 to 3 carbon atoms and R is hydrogen or alkyl groups having 1 to 2 carbon atoms. As examples of compounds having the above formula there may be named trimethyl trimesate, tetramethyl pyromellitate, tetramethyl mello phonate, trimethyl hemimellitate, trimethyl trimellitate, tetramethyl prehnitate, and the like. In addition, there may be employed mixtures of the above esters which are obtained in practical synthesis. That is, in most instances when preparing any of the compounds having the above formula, other related compounds having the same for-1 mula may be present in small .amounts as impurities. This does not aliect'the' compound as a chain-branching agent in the preparation of the modifiedpolyesters and h i nch n l e s o s l nk a en y be employed inthe preparation of the polyesters and polyesters in amounts ranging from 0.05 mol percent to; 2.4 mol percent, based on the amount of dicarboxylic acid or dialkyl ester thereof employed in the reaction mixture. The preferred range of chain-branching agent for use in the present invention is from 0.1 to 1.0 mol percent. 1 In the practice of the present invention, the calculated amounts of chain-terminating agent or chain-terminating agent and chain-branching agent or cross-linking agent are charged to the reaction vessel at the beginning of the first stage of the esterification reaction and the reaction proceeds as in any well-known esterification polymerization. The first step or stage of the reaction is carried out at atmospheric pressure and at a temperature in the range of 90 C. to 250 C. and preferably between 150 and 220 C. when from 0.001 to 1.0 percent by weight, based on the weight of the dicarboxylic acid or ester thereof, of a suitable esterific-ation catalyst, such as manganous form-ateior zinc acetylacetonate, isemployed. If de-.

sired, the reaction may be carried out at pressures above or below atmospheric. Methanol is'evolved which is continuously removed 'by distillation. At the completion of the first stage, the excess glycol, any, is distilled oif prior to entering the second stage of the reaction.

. .In the second or polymerization stage, the reaction -is conducted at reduced pressures and preferably in the presence of an inert gas, such as nitrogen, in order to prevent oxidation. This can be accomplished by maintaining a nitrogen blanket over the reactants, said nitrogen containing less than 0.003 percent oxygen. For optimum results, a pressure within the range of less than 1 mm.

up to 5 mm. of mercury is employed. This reduced pressure is necessary to remove the free ethylene glycol that is'formed during this stage of the reaction, the ethylene glycol being volatilized under these conditions and removed from the system. The polymerization step is conducted at a temperature in the range of 220 to 300 C. This stage of the reaction may be eifected either in the liquid, melt or solid phase. In the liquid phase, particularly, reduced pressures must be employed in order to remove the free ethylene glycol which emerges from the polymer as a result of the condensation reaction.

In the preparation of the described polyesters, the stage of the reaction takes place in' approximately to 2 hours, when employing a suitable. esten'fication catalyst. In the absence of a catalyst, times up to 6 hours may be necessary in order to complete this phase of the reaction. In the second stage, a reaction time of approximately 1 to 4 hours may be employed with a time of 1' to 3 hours being the optimum, depending on catalyst concentration, temperature, viscosity desired, amount of color allowable in the finished polymer, etc.

The modified linear condensation polyesters, produced in accordance with the present invention, have a specific viscosity in the range of 0.30 to 0.60, which represents the fiberand filament-forming polymers-I It'is to be understood, of course, that non-fiber-forming polyesters may be produced by means of the present invention, which have a specific viscosity greater or less than that reiterated above and such polyesters are useful, for example, in the manufacture of coating compositions, lacquers, molding compositions, and the like.

If it is desired to produce shaped afticles from the polyester solutions of the present invention which have a modified appearance or modified properties, various agents to accomplish these effects may be added to the polyester solutions of this'invention prior to the fabrication of the articles without any ill efiects thereo'n, Such added agents might be plasticizers, pigments, dyes, anti-static agents, fire-retarding agents, etc.

The following examples are intended to illustrate the new compositions of the invention more fully, but are not intended to limit the scope of the invention, forv it is possible to eifect many modifications therein. In the examples, all parts and percents are by weight unless otherwise indicated.

Example I 9 grams of tris (dirnethylamido) phosphate and 1 gram of polyethylene terephthalate were mixed together and warmed with stirring to 175 C. where the polymer readily dissolved, yielding a clear fiuid solution suitable for; both wet and dry spinning. On cooling, the solution solidified at 110 C. but was easily redissolved upon the application of heat. The solution was stable to temperatures above 120 C.

Example 11 There was charged to a reaction vessel 82 grams dimethyl terephthalate, 106.2 grams of ethylene glycol" (approximately 88 ml.) and 8.2 grams of 'ethoxypoly-f' ethylene glycol having an average'molecular weight of about 3050 (10.5 mol percent based on the molsof di-' methyl terephthalate).

lution was 'efiected. The mixturewas maintainedat temperature for 90 minutes to etfect the ester interchange reaction.- Thereafter, the temperature was raised to 225 C. to remove excess ethylene glycol and maintained at that temperature under a vacuum of less than 1 mm; of mercury for 3 hours to elfect polymerization. There wasobtained a high molecular Weight polyester having a melting'point of about 255 C. and a specific viscosity of about 0.3. 1 gram of the polyester so prepared and 9 grams of tris (dimethylamido) phosphate were mixed together and warmed with stirring at 175 C.where the" polymer readily dissolved yielding a clear fluid solution suitable for the formation of fibers by both Wet and dry spinning methods. tures above 120 C.

' Example III 9 grams of his (dimethylamido) methane phosphonate and 1 gram of polyethylene terephthalate Weremixed together and warmed with stirring to 180 C. where the polymer readily dissolved yielding a clear fluid"solutiori suitable for both wet and dry spinning. On cooling, the solution became hazy at 100 C. and solidified at C. but was readily. redissolved upon application of heat.

The solution was stable to temperatures above C.

Example IV 9 grams of his (dimethylamido) methane phosphonate and 1 gram of the modified polyester prepared as in Example II were mixed together and warmed with stirring at 170 C. where the polymer readily dissolved, yielding a clear fluid solution suitable for both wet and dry spin-' ning. The solution was stable to temperatures above C.

Example V- V There was charged to a reaction vessel 82; grams of,

drmethyl terephthalate, 106.2 grams of ethylene glycol (approximately 88 ml.) and 8.2 grams of ethoxypoly'.

ethylene glycol having an average molecular weight of about 3050. Subsequently, 40 mg. of manganous formate were added to the reaction vessel. The reactants were well mixed and heated at 177 C. until solution was efiected. The reactants were then maintained at this temperaturefor 90 minutes to effect an ester interchange reaction. Thereafter, the temperature was raisedto 285 C. to remove excess ethylene glycol and maintained at that point under a vacuum of less than 1 mm.

of mercury for 3 hours to-etfect polymerization. There Subsequently, 40mg. of man-' ganous fo'rmate was added to the reaction vesseh The: reactants were Well mixed and heated at 177 C. untilso- The solution was stable to tempera} C. in air and having a;

ExampleVI '8 grams of tris (dimethylamido) phosphate and .2 grams of polyethylene terephthalate'were mixed together and warmed with stirring at 170 C. where the polymer readily dissolved yielding a clear fluid solution suitable for both wet and dry spinning. The solution was stable va uenes a ov 9 6-.

'- V 7 Example VII There was charged to a reaction vessel 100 grams of dimethyl terephthalate, 120 grams of ethylene glycol and grams of methoxypolyethylene glycol having an average molecular weight of about 2000 (.98 mol percent based onthe mols of dimethyl 'terephthalate). Thereafter, 0.16 gram of pentaerythn'tol was added to the reaction =ves sel and 0.065 gram of zinc acetylacetonate catalyst was added to the reactants. The reactants were well mixed and heated for approximately 8 6 minutes at atmospheric pressure and a temperature gradually from il 56 C. to 190 C. until solution was effected. Subsequently, the temperature was raised to 240 C. for approximately 44 minutes and at atmospheric pressure to remove excess glycol. Then the temperature was raised from 240 C. to 280 C. over -a period of 42 minutes while the pressure was gradually decreased to 1 mm. of mercury and maintained at about 280 C. for approximately 2 hours to efiect polymerization. There was obtained a high molecular weight polyester having a melting point of about 255 C. and a specific viscosity of 0.40 at C. calculated in a 2 to 1 mixture of phenol trichlorophenol containing 0.5 percent by weight of polymer. 0.50 gram of the polyester so prepared and 9.50 grams of his (dimethylamido) phosphate were mixed together and warmed with stirring to 165 C. where the polymer readi- 1y dissolved yielding a clear fluid solution suitable for the formation of fibers by both wet and dry spinning methods. The solution was stable to temperatures of 100 C. where it became slightly turbid. I

Example VIII 2.5 grams of the polyester as prepared in Example VII were mixed with 7.5 grams of his (dimethylamido) methane phosphate and warmed with stirring to 175 C. where the polymer readily dissolved yielding a clear fluid relatively viscous solution suitable for the preparation of film. The solution became slightly turbid around 150" C. The solution was stable to temperatures of about 135-140 C. A film cast from such solution appeared to have good strength.

Example IX 2 grams of the polymer prepared by the process of Example VII and 8 grams of tris (dimethylamido) phosphate were mixed together and warmed with stirring to 185 C. where the polymer readily dissolved yielding a clear fluid solution suitable for the formation of fibers by both wet and dry spinning methods. Slight turbidity appeared in the solution at about. 145 C. The solution was stable to temperatures above 130 C. Fibers extruded therefrom were readily cold drawable and had good tensile strength.

The polyester compositions of this invention can be usefully employed in the coating field, for example, in the coating of textile fabrics. Thus,.a fabric can be coated and/or impregnated with the polyester solutions described herein and then treated, that is soaked, in a non-solvent for the polyester in order to precipitate the polyester in and on the fabric. Metals, paper and impervious films mayalso be coated with the polyester compositions, of this invention by conventional and well-known procedures.

One of the principaladvantages of the instant invention is'that it provides polyester compositions which are readily convertible to useful shaped articles by the wet or dry spinning methods which are more economical than 8 the melt-spinning method. Numerous other advantages of this invention will be apparent to those skilled in the art fiom reading the instant description.

As many apparently widely different embodiments of this invention may be made'without departing from the spirit and scope thereofi'it is to be understood that the same is not to be' limited to the specific embodiments therwf, except as defined in the appended claims. 1

e We claim: y

'1, .A new composition of matter comprising a homogeneous, miscible mixture of a synthetic linear condensation polyester and a solvent having the formula:

, O H: v wherein R is selected from the group consisting of CH 7 (CE):N/ said polymester being selected from the group consisting of (A) polyesters formed by the reaction of at least one dicarboxylic acid and at least one glycol of the formula HO(CH -'-OH, wherein n is an integer from 2 to -10, and wherein all the glycols employed have the said formula HO'(CII OH, (B) the polyesters of (A) modified by a chain terminator selected from the group con-' sisting of polyalkylvinyl ethers having one terminal hydroxyl group wherein the alkyl group contains from '1 to 4 carbon atoms, and compounds having the formula:

wherein R is selected from the group consisting of alkyl groups containing 1 to 18 carbon atoms and aryl groups containing 6 to 10 carbons atoms, m and n are integers from 2 to 22, and x is an integer from 1 to 100, indicative of the degree of polymerization, and (C) the polymesters of (B) modified by a chainbranching agent selected from the group consisting of pentaerythritol, compounds hav-- ing the formula: V

R--l(0H) wherein R is an alkylene group containing from 3 to 6' carbon atoms and n is an integer from 3 to 6, and compounds having the formula:

' R---(CH OH) 3 wherein R is an alkylene group containing from 2 to 6 carbon atoms, compounds having the formula:

CH nOH L( I) 3 wherein n is an integer from 1 to 6, and compounds having the formula:

wherein R, R and R" are alkyl groups containing 1 to 3 carbon atoms and R"? is selected from the group consisting of hydrogen, methyl and ethyl radicals.

2. A new composition of matter as definedin claim 1 wherein the polyester is polyethylene terephthalate.

"T9 3. A new composition ofmatter as defined in claim 1 wherein the solvent is his (dimethylamido) methane phosphonate. V V I I a 4. A- new-composition of matter as, definedin claim 1 wherein the solvent is tris (dimethylamido) phosphate. -5. A new composition of matteras defined in claim 1 wherein the solvent is tetrakis (dimethylamido) pyrophos- 6. A new composition of matter as defined in claim 1 wherein the chain terminator isethoxypolyethylene glycol.

7. A new composition of matter 'as-defined in claim 1 wherein 'the chainlterminator is hydroxy polyvinylmethyl smea v 8'. A new composition of matter as defined in claim 1 wherein the chain terminator is methoxypolyethylene glycol.

9. A new composition of matter as defined in claim 1 wherein the chain terminator is propoxypolyethylene glycol.

10. A new composition of matter as defined in claim 1 wherein the chain-branching agent is trimethyl trimesate.

11. A new composition of matter as defined in claim 1 wherein the chain-branching agent is pentaerythritol.

12. A new composition of matter as defined in claim 1 wherein the chain branching agent is tripropyl trimesate.

13. A new composition of matter as defined in claim 1 wherein the chain-branching agent is glycerol.

"14. A new composition of matter comprising a homogeneous, miscible mixture of a synthetic linear condensation polyester and a solvent having the formula:

C CHs wherein R is selected from the group consisting of CR3, 3 and (CHsh-N said polyester being selected from the group consisting of (A) polyesters formed by the reaction of at least one dicarboxylic acid and at least one glycol of the formula HO(CH OH, wherein n is an integer from 2 to 10, and wherein all the glycols employed have the said formula HO(CH,) OH, (-B) the polyesters of (A) modified by a chain terminator selected from the group consisting of polyalkylvinyl ethers having one terminal hydroxyl group wherein the alkyl group contains from 1 to 4 carbon atoms, and compounds having the formula:

wherein R is selected from the group consisting of alkyl groups containing 1 to 18 carbon atoms and aryl groups containing 6 to 10 carbon atmos, m and n are integers from 2 to 22, and x is an integer from 1 to 100, indicative of the degree of polymerization, and (C) the polyesters of (B) modified by a chain-branching agent selected from the group consisting of pentaerythritol, compounds having the formula:

wherein R is an alkylene group containing from 3 to 6 carbon atoms and n is an integer from 3 to 6, and compounds having the formula:

(III) 2 )a wherein R is an 'alkylene group containing from 2 to 6 carbon atoms, compounds having the formula:

r CHJ);10H I.

'10 wherein n is an; integer from 1 to 6,- and compoundshav. ingtheformula: I v- I i I Q- O-R' 11-0-0 wherein R, R and R are alkyl groups containing 1 to 3 carbon atoms and R" is selectedfron ilre group consisting of hydrogen, methyl and ethyl radicals, said solvent being employed in a range of 75 to 95 percent, based on the total weight of the composition.

15. A new fiber-forming composition comprising a solvent of the formula:

CH: CH: wherein R is selected from the group consisting of CH;,, N(CH and (CHsh-N O l o (CHzOr-N said polyester being selected from the group consisting of (A) polyesters formed by the reaction of at least one dicarboxylic acid and at least one glycol of the formula HO(CH ),',-OH, wherein n is an integer from 2 to 10, and wherein all the glycols employed have the said formula HO(CH ),,-OH, (B) the polyesters of (A) modified by a chain terminator selected from the group consisting of polyalkylvinyl ethers having one terminal hydroxyl group wherein the alkyl group contains from 1 to 4 carbon atoms, and compounds having the formula:

wherein R is selected from the group consisting of alkyl groups containing 1 to 18 carbon atoms and aryl groups containing 6 to 10 carbon atoms, m and n are integers from 2 to 22, and x is an integer from 1 to 100, indicative of the degree of polymerization, and (C) the polyesters of (B) modified by a chain-branching agent selected from the group consisting of pentaerythritol, compounds having the formula:

wherein R is an alkylene group containing from 3 to 6 carbon atoms and n is an integer from 3 to 6, and compounds having the formula:

n 171 y wherein k is an alkylene group Containing fi'omQ to carbon atoms, compounds having the formula: 1

CH nOH 2) v r V wherein n is an integer froml to 6, and compounds having the formula:

wherein R; R"iid R" areafkyt groups eontaining 1m 3 earbon atoms and R is selected from the group consisfing of hy drogen, methyl and ethyl radicals, and heating the mixtnr'e -af1a t'empelfgtnre in the-range of 140? Cito the boiling point of the mixture;

17; A pregess as fd'efined in ,cl-aini IG-wherein the 501- Vent is*bis (din'i ethylamido) methane phosphonate;

-1 8, A process as defined in claim 16 wherein thesol-- vent isietrakisf(dimeihylnmido)pyrophosphate;' '20. The process as defined in claim 16 wherein the polyester is polyethylene terephthalate having a molecular weight of at least 10,000.

No references cited.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2 952 652 Arthur B. Beindorff et 31.

It is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3 line 2 for "draining" read drawing column 9 line 37, for "CR read CH column l2, line 4,

for "at" read to o (SEAL) Attest:

ERNEST .SWIDER Attesting Oflicer ARTHUR W. CROCKER Acting Commissioner of Patents September 13 196 

1. A NEW COMPOSITION OF MATTER COMPRISING A HOMOGENEOUS, MISCIBLE MIXTURE OF A SYNTHETIC LINEAR CONDENSATION POLYESTER AND A SOLVENT HAVING THE FORMULA: 